fix: don't require capitalised DOCTYPE

it is case insensitive: https://html.spec.whatwg.org/multipage/syntax.html#the-doctype

Author: danielroe

docs/content/en/index.md

@@ -94,12 +94,13 @@ This module configures [`html-validate`](https://html-validate.org/) to automati
          rules: {
            'svg-focusable': 'off',
            'no-unknown-elements': 'error',
-           // Conflicts or not needed when using prettier formatting
+           // Conflicts or not needed as we use prettier formatting
            'void-style': 'off',
            'no-trailing-whitespace': 'off',
            // Conflict with Nuxt defaults
            'require-sri': 'off',
            'attribute-boolean-style': 'off',
+           'doctype-style': 'off',
            // Unreasonable rule
            'no-inline-style': 'off'
          }

src/config.ts

@@ -16,6 +16,7 @@ export const defaultHtmlValidateConfig: ConfigData = {
     // Conflict with Nuxt defaults
     'require-sri': 'off',
     'attribute-boolean-style': 'off',
+    'doctype-style': 'off',
     // Unreasonable rule
     'no-inline-style': 'off'
   }